Bernie Sanders has built more than just a following. He’s amassed the mother of all email lists. Some estimate it contains more than 5 million contacts, which is big, even by presidential standards. That database has allowed Sanders to raise thousands of dollars at the click of a button. But as his candidacy coasts to a close (?), some of his supporters say they want off before the Vermont senator shares their names with the Clinton campaign—or worse yet, the Democratic National Committee.

One such supporter is a software engineer from Los Angeles. Six months ago, he signed up to canvass for the Sanders campaign. A private person, he nonetheless handed over his personal information, figuring it was the price of helping out a candidate he supports. But on the day before the California primary, he posted a plea on Reddit that was upvoted more than 4,000 times: “Senator Sanders, Please DO NOT give my info to Hillary or the DNC.”

I just saw something on MSNBC where Mr. Mook [Clinton’s campaign manager] said they are reaching out to Sanders’ campaign for their support and help/assistance. Now, I can't speak for the rest of the Sanders' supporters, but I will tell you that I only came out for Bernie and have always kept my distance from providing too much information to the DNC.

So, please Bernie, don't give them my personal data. Thanks.

“I just want to sort of be able to go back into the telephone booth and change back into my regular clothes and go back into my life,” the redditor said later in a phone interview, who asked to remain anonymous for the same reasons why he doesn’t want his personal data shared with other campaigns. “I was hesitant to give out any data, and so the data I did give out, like so many other things, was done early on in the process, naively.”

His beef isn’t with Hillary Clinton, though he doesn’t like her. He’s more concerned about the long-term security of his personal metadata. Many of the other commenters chiming in beneath his post expressed deep ambivalence toward Clinton and the DNC, though, which some Sanders supporters believe has treated their candidate unfairly. “If the DNC contacts you, just tell them they should ask Wall Street for money,” one poster wrote.

The Sanders campaign didn’t respond to a request for comment about the future of the supporter list. Speculation abounds. Senate Minority Leader Harry Reid reportedly asked the campaign last month to deploy the list to assist Democrats in Senate races, but was rebuffed by Jeff Weaver, Sanders’s campaign manager. Liberal groups have said they’d love to take a peek at the Vermont senator’s data.

People affiliated with the campaign have pushed back. On Monday, a fundraiser manager for Revolution Messaging, the D.C.-based firm Sanders has employed to manage his campaign data, tweeted that the senator’s list was like King Arthur’s Excalibur: “Lots of people might think they can use it, but it takes someone special for it to work.”

You don’t just email The List and then all of a sudden drown in money.

Could Sanders transfer his list to the DNC? Probably. If he wanted, he could hand it over to Donald Trump. His campaign website’s privacy policy reserves the right to share supporters’ information with “groups, causes, organizations, or candidates we believe have similar views, goals, and principles.”

But would he? Probably not, said Amelia Showalter, the former director of digital analytics for the Obama campaign. While Republicans have a reputation for sharing voter lists, Democrats do not. “No digital expert would ever recommend outright selling off a list,” she said. “I think it would be extremely unlikely for the Sanders campaign to say, ‘Here, DNC, Hillary—here are all of my email addresses.’”

Showalter thinks it’s more likely Sanders will follow the lead of Obama for America, which used the campaign’s influential voter list to build Organizing For Action, an independent group that continued on after the president’s 2012 victory. Howard Dean’s campaign transformed along similar lines in 2004, birthing Democracy for America.

One way or another, that data will definitely stick around on a campaign server. “Obviously, when someone interacts with a campaign in any way, that goes into a database,” Showalter said. “That’s exactly what you’d want a good, smart campaign to do.”

The average Sanders donor might be most concerned about his or her contribution information, which is stored not only with the campaign but also ActBlue, a Political Action Committee Sanders uses to process payments (as do many other Democrats). Erin Hill, ActBlue’s executive director, assured me that data would be kept private, at least on her end. “We don't pass along data or any other information to other organizations,” she said. “Those are decisions that campaigns will make between themselves.”

The cost of the connected age, of course, is that a person can never truly be sure where their data will end up. Once surrendered to an online retailer, a credit-card number can be stolen; a hacked password can find itself on the dark web. In the same way, a candidate’s email list lasts forever, by design. It will not languish in obscurity like an old MySpace account. It will be used again and again. A campaign supporter can only hope it remains in good hands.

That may seem chilling to someone once captivated by Bernie Sanders who now wants to fade back into anonymity. “I was barely willing to take that risk with the Sanders campaign. That was the cost of participation,” said the L.A. redditor. “But [Clinton] doesn’t get me over the hurdle. The Democratic Party definitely doesn’t get me over the hurdle.”

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